http: catch panics

R=rsc
CC=golang-dev
https://golang.org/cl/4559067

src/pkg/http/serve_test.go

@@ -13,6 +13,7 @@ import (
 	. "http"
 	"http/httptest"
 	"io/ioutil"
+	"log"
 	"os"
 	"net"
 	"reflect"
@@ -432,6 +433,9 @@ func TestSetsRemoteAddr(t *testing.T) {
 }
 
 func TestChunkedResponseHeaders(t *testing.T) {
+	log.SetOutput(ioutil.Discard) // is noisy otherwise
+	defer log.SetOutput(os.Stderr)
+
 	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
 		w.Header().Set("Content-Length", "intentional gibberish") // we check that this is deleted
 		fmt.Fprintf(w, "I am a chunked response.")
@@ -755,6 +759,20 @@ func TestZeroLengthPostAndResponse(t *testing.T) {
 	}
 }
 
+func TestHandlerPanic(t *testing.T) {
+	log.SetOutput(ioutil.Discard) // is noisy otherwise
+	defer log.SetOutput(os.Stderr)
+
+	ts := httptest.NewServer(HandlerFunc(func(ResponseWriter, *Request) {
+		panic("intentional death for testing")
+	}))
+	defer ts.Close()
+	_, err := Get(ts.URL)
+	if err == nil {
+		t.Logf("expected an error")
+	}
+}
+
 func BenchmarkClientServer(b *testing.B) {
 	b.StopTimer()
 	ts := httptest.NewServer(HandlerFunc(func(rw ResponseWriter, r *Request) {

src/pkg/http/server.go

@@ -6,12 +6,12 @@
 
 // TODO(rsc):
 //	logging
-//	post support
 
 package http
 
 import (
 	"bufio"
+	"bytes"
 	"crypto/rand"
 	"crypto/tls"
 	"fmt"
@@ -20,6 +20,7 @@ import (
 	"net"
 	"os"
 	"path"
+	"runtime"
 	"strconv"
 	"strings"
 	"sync"
@@ -475,6 +476,33 @@ func (c *conn) close() {
 
 // Serve a new connection.
 func (c *conn) serve() {
+	defer func() {
+		err := recover()
+		if err == nil {
+			return
+		}
+		c.rwc.Close()
+
+		// TODO(rsc,bradfitz): this is boilerplate. move it to runtime.Stack()
+		var buf bytes.Buffer
+		fmt.Fprintf(&buf, "http: panic serving %v: %v\n", c.remoteAddr, err)
+		for i := 1; i < 20; i++ {
+			pc, file, line, ok := runtime.Caller(i)
+			if !ok {
+				break
+			}
+			var name string
+			f := runtime.FuncForPC(pc)
+			if f != nil {
+				name = f.Name()
+			} else {
+				name = fmt.Sprintf("%#x", pc)
+			}
+			fmt.Fprintf(&buf, "  %s %s:%d\n", name, file, line)
+		}
+		log.Print(buf.String())
+	}()
+
 	for {
 		w, err := c.readRequest()
 		if err != nil {